2-(aminomethyl)-1-cyclopentylamine (AMC) was first reported by Lazier and Howk, described in U.S. Pat. No. 2,292,949, who prepared the diamine by hydrogenation of CPI at 2000-3000 psi H2, 120° C. using either a nickel on alumina or finely divided, unsupported cobalt catalyst. The yield using Ni was 36% and 59% using Co. A hydrogen gas pressure of at least 1500 psi was used for the reaction in the presence of a Group VIII metal catalyst.
In GB 1397576 Chabert describes a process for the catalytic hydrogenation of CPI in the presence of a powdered Raney-type catalyst containing 22-43% nickel, 0.2-1.8% chromium, 1.5-5% iron with the balance being aluminum and incidental impurities. The process is run in aqueous sodium hydroxide and ethanol at 93° C. and a hydrogen pressure of 1160-1305 psi. The yield of AMC is 54%.
Klenke and Gilbert, Journal of Organic Chemistry, (2001), 66, 2480-2483 disclose a method for the reduction of nitrites in the presence of Boc-protected amines using combinations of nickel with palladium on carbon. This reference does not disclose the use of these catalyst combinations to reduce 2-iminonitriles to their corresponding diamines, nor does it disclose the use of a palladium-doped Raney-type nickel for such a conversion.
AMC is a valuable molecule that is useful in the formulation of epoxy-curing agents for polyurethane cross-linkers, for polyamide modifiers, for metal chelating agents and a host of other uses. AMC has been produced from CPI by various catalytic hydrogenation methods. Most of these prior art methods require high pressures of hydrogen, high levels of corrosive sodium hydroxide, or results in low AMC purity and/or yield.
It is the object of the present invention to provide a process for the high yield manufacture of AMC which is economical and which uses relatively low pressure of hydrogen, eliminating the use of high levels of aqueous sodium hydroxide. The combination of these improvements to AMC manufacture affords an easier operation and lower overall cost of production.